Heat transfer compositions with high electrical resistance for fuel cell assemblies

ABSTRACT

The present invention relates generally to heat transfer compositions. More particularly, the present invention relates to heat transfer compositions with high electrical resistance for use in power-generating equipment or in engines. Such compositions are particularly useful in fuel cell assemblies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Application No. 60/358,201, filed Feb. 19, 2002.

FIELD OF THE INVENTION

The present invention relates generally to heat transfer compositions.More particularly, the present invention relates to heat transfercompositions with high electrical resistance for use in power-generatingequipment or in engines. Such compositions are particularly useful infuel cell assemblies.

BACKGROUND OF THE INVENTION

Heat transfer fluids (e.g., coolants) for internal combustion engines(“ICEs”) are known. Such fluids commonly contain about 50% water and 50%ethylene glycol (by weight) with trace amounts of additives, includingcorrosion inhibitors. However, the ICE may be obsolete within the comingdecades. Fuel cells have emerged as a potential replacement. In general,a fuel cell is an electrochemical device that converts the chemicalenergy of a fuel into electrical energy. They provide several advantagesover ICE. Fuel cells are more efficient in extracting energy from fuel(e.g., 60-70% efficiency as compared to 40% for turbodiesel engines and30% for gasoline engines). Further, fuel cells are quiet and producenegligible emissions of pollutants. Also, the primary fuel source forthe fuel cell is hydrogen, which is more readily available than ICE fuelsources (e.g., gasoline). However, replacement of the ICE with fuelcells may require the concomitant replacement of known heat transferfluids.

Typically, a fuel cell consists of an anode (a positively chargedelectrode), a cathode (a negatively charged electrode) and anelectrolyte in between the two electrodes. Each electrode is coated witha catalyst layer. At the anode, a fuel, such as hydrogen, is convertedcatalytically to form cations, which migrate through the electrolyte tothe cathode. At the cathode, an oxidant, such as oxygen, reacts at thecatalyst layer to form anions. The reaction between anions and cationsgenerates a reaction product, electricity and heat.

The current produced in a fuel cell is proportional to the size (area)of the electrodes. A single fuel cell typically produces a relativelysmall voltage (approximately 1 volt). To produce a higher voltage,several fuel cells are connected, either in series or in parallel,through bipolar plates separating adjacent fuel cells (i.e., “stacked”).As used herein, a fuel cell assembly refers to an individual fuel cell.

The most common fuel and oxidant used in fuel cells are hydrogen andoxygen. In such fuel cells, the reactions taking place at the anode andcathode are represented by the equations:Anode reaction: H₂→2H⁺+2e ⁻  (1)Cathode reaction: ½ O₂+2H⁺+2e ⁻→H₂O  (2)The oxygen used in fuel cells comes from air. The hydrogen used can bein the form of hydrogen gas or a “reformed” hydrogen. Reformed hydrogenis produced by a reformer, an optional component in a fuel cellassembly, whereby hydrocarbon fuels (e.g., methanol, natural gas,gasoline or the like) are converted into hydrogen. The reformationreaction produces heat, as well as hydrogen.

Currently, there are five types of fuel cells, categorized by theirelectrolyte (solid or liquid), operating temperature, and fuelpreferences. The categories of fuel cells include: proton exchangemembrane fuel cell (“PEMFC”), phosphoric acid fuel cell (“PAFC”), moltencarbonate fuel cell (“MCFC”), solid oxide fuel cell (“SOFC”) andalkaline fuel cell (“AFC”).

The PEMFC, also known as polymer electrolyte membrane fuel cell, uses anion exchange membrane as an electrolyte. The membrane permits onlyprotons to pass between the anode and the cathode. In a PEMFC, hydrogenfuel is introduced to the anode where it is catalytically oxidized torelease electrons and form protons. The electrons travel in the form ofan electric current through an external circuit to the cathode. At thesame time, the protons diffuse through the membrane to the cathode,where they react with oxygen to produce water, thus completing theoverall process. PEMFC's operate at relatively low temperatures (about200° F.). A disadvantage to this type of fuel cell is its sensitivity tofuel impurities.

The PAFC uses phosphoric acid as an electrolyte. The operatingtemperature range of a PAFC is about 300-400° F. Unlike PEMFC's, PAFC'sare not sensitive to fuel impurities. This broadens the choice of fuelsthat they can use. However, PAFC's have several disadvantages. Onedisadvantage is that PAFC's use an expensive catalyst (platinum).Another is that they generate low current and power in comparison toother types of fuel cells. Also, PAFC's generally have a large size andweight.

The MCFC uses an alkali metal carbonate (e.g., Li⁺, Na⁺ or K⁺) as theelectrolyte. In order for the alkali metal carbonate to function as anelectrolyte, it must be in liquid form. As a result, MCFC's operate attemperatures of about 1200° F. Such a high operating temperature isrequired to achieve sufficient conductivity of the electrolyte. Itallows for greater flexibility in the choice of fuels (i.e., reformedhydrogen), but, at the same time, enhances corrosion and the breakdownof cell components.

The SOFC uses a solid, nonporous metal oxide as the electrolyte, ratherthan an electrolyte in liquid form. SOFC's, like MCFC's, operate at hightemperatures, ranging from about 700 to about 1000° C. (1290 to 1830°F.). The high operating temperature of SOFC's has the same advantagesand disadvantages as those of MCFC's. An additional advantage of theSOFC lies in the solid state character of its electrolyte, which doesnot restrict the configuration of the fuel cell assembly (i.e., an SOFCcan be designed in planar or tubular configurations).

The final type of fuel cell, known as AFC, uses an aqueous solution ofalkaline potassium hydroxide as the electrolyte. Their operatingtemperature is from about 150 to about 200° C. (about 300-400° F.). Anadvantage to AFC's is that the cathode reaction is faster in alkalineelectrolytes than in acidic electrolytes. However, the AFC is verysusceptible to contamination, so it requires pure reactants, i.e., purehydrogen and oxygen.

In general, the reactions that take place within the fuel cell assembly(i.e., the electrochemical reaction and the reformation reaction) areexothermic. However, the catalyst employed in these reactions issensitive to heat. To perform optimally, fuel cells should be maintainedat a certain temperature that is nearly uniform across each cell in thestack. For example, at high temperatures, the catalyst may be destroyed,while at low temperatures, ice may form within the fuel cell assembly.Thus, to accommodate such temperature requirements, heat transfercompositions are needed.

Known heat transfer compositions are not amenable for use in fuel cellassemblies. Conventional heat transfer fluids contain corrosioninhibitors, which are generally metal or organic acid salts. Such saltsexist as ions in solution. The presence of significant amounts ofpositive and negative ions in solution provides a path for a “strayelectrical current.” Such stray current must be limited for severalreasons. First, it may cause electrical shock hazards to the fuel celloperator. Second, such stray current may generate highly explosivehydrogen gas in the cooling system from hydrolysis. Lastly, asignificant portion of the electricity generated by the fuel cell may beshorted through the fluid, rather than going to power production,thereby decreasing the efficiency of the fuel cell assembly. Thus, heattransfer fluids used in a fuel cell application must have lowerelectrical conductivities (i.e., higher electrical resistance) thanthose used in an ICE application.

In addition to electrical resistivity, there are additionalconsiderations involved in the development of fuel cell heat transferfluids. One consideration relates to their application. Fuel cell heattransfer fluids in an automotive application will likely be exposed tometals different from those in an ICE. For example, fuel cell assembliesare expected to contain stainless steel, some aluminum alloys, speciallycoated aluminum and insulating polymers, whereas ICE contain cast iron,steel, brass, solder and copper. Thus, the fuel cell heat transferfluids must accommodate different types of metals. Another considerationrelates to the physical properties of the heat transfer fluid. In fuelcells, the heat transfer fluid must be able to flow through the assemblyin order to maintain uniform temperature across the catalyst layer. Thisdepends on the heat transfer fluid's freezing point, vapor pressure,viscosity, pumpability and laminar flow. In addition to theseproperties, the ability of the heat transfer fluid to adsorb gasesaffects the conductivity of the heat transfer fluid. As a finalconsideration, fuel cell heat transfer fluids, like known heat transferfluids, must be cost effective.

In general, water or deionized water have been used as the heat transferfluid in fuel cell applications. See, U.S. Pat. Nos. 5,252,410;4,344,850; 6,120,925; and 5,804,326. However, there are severaldisadvantages to using water as a fuel cell heat transfer fluid. First,a fuel cell may be exposed to extremes in environmental conditions,e.g., broad ranges in temperatures. For example, when the operatingtemperature of the fuel cell falls below the freezing point of water,the volumetric expansion of water may cause severe damage to the fuelcell. In addition, water may be corrosive to the different metals thatare used in fuel cell applications. As a result, inorganic and/ororganic inhibitors would be needed to provide long term corrosionprotection. However, such inhibitors may change the electricalresistance of the heat transfer fluid. Lastly, the electricalconductivity of water may change over time as a result of accumulatingdegradation contaminates, by-products, and rust. Each of the above isdetrimental to fuel cell performance.

Efforts at maintaining the temperature above the freezing point of thewater heat transfer fluid have focused on the design of the fuel cellassembly. For example, U.S. Pat. No. 6,248,462 B1 (“the '462 patent”)discloses a fuel cell stack that contains a cooler plate interspersedthroughout the fuel cell stack. The cooler plate circulates anantifreeze solution through its channels. Such cooler plate prohibitsthe diffusion of antifreeze into the rest of the fuel cell stack. Whilethe cooler plate addresses the first problem associated with using wateras a heat transfer fluid, it fails to obviate them all. Moreover, theaddition of such a cooler plate to the fuel cell stack increases theoverall weight and volume of the fuel cell stack.

Efforts to address these shortcomings have focused on the development offuel cell assemblies that accommodate known antifreezes. For example,U.S. Pat. No. 6,316,135 B1 and International Publication No. WO 01/47052A1 disclose a fuel cell assembly using only antifreeze as the heattransfer fluid. Such fuel cell assemblies contain certain “wetproofed,”i.e., substantially hydrophobic, components. The design of theseassemblies prevents the antifreeze from contaminating the electrolyteand the catalyst, thereby eliminating the need to isolate the antifreezefrom the components of the fuel cell assembly (e.g., in a cooler plate).As a result, fuel cell stacks can be made having lower weight and volumethan those disclosed in the '462 patent. However, such fuel cellassemblies have several problems, including antifreeze contamination andreduced cooling effectiveness caused by the wetproofed materials.

New heat transfer fluids have also been developed. For example, each ofU.S. Pat. Nos. 5,868,105; 6,101,988; 6,053,132; and 6,230,669 disclose aheat transfer fluid that is a substantially anhydrous, boilable liquidhaving a saturation temperature higher than that of water. The disclosedheat transfer fluids have a minimum content of water, for example, lessthan 5% by weight. An example of one such heat transfer fluid ispropylene glycol with additives to inhibit corrosion. The use ofpropylene glycol as a heat transfer fluid suffers limitations. Oneimportant limitation lies in its viscosity. At low temperatures,propylene glycol is highly viscous. This reduces its flow through thefuel cell assembly, and consequently, its heat removal efficiency. Theend result is a decrease in the efficiency of the fuel cell assembly.

Mixtures of water and alcohols have also been used as fuel cell heattransfer fluids. See, e.g., Japanese Patent Laying-Open Gazette No.7-185303. Such mixtures suffer from deficiencies resulting from solventvaporization. Alcohols, like methanol, may cause some of the heattransfer fluid to vaporize into the cooling layer. Such vaporizationraises the pressure of the cooling layer, thereby preventing the heattransfer fluid from flowing at a constant rate through the fuel cellassembly. This effects the ability of the heat transfer fluid tomaintain a uniform temperature across the catalyst layer.

Other fuel cell heat transfer fluids have also been used. For example,water-glycol mixtures, Thenninol D-12 (which is a hydrotreated heavynaphtha (petroleum)) and dielectric fluids (e.g., mineral oils andsilicone oils) have been used in fuel cells. See, e.g., U.S. Pat. Nos.5,565,279; 5,252,410; 5,804,326; and 6,218,038. The fuel cell heattransfer fluid disclosed in International PCT Publication WO 01/23495comprises water, glycol and corrosion inhibitors. Each of the heattransfer fluids above has deficiencies, including flammability andincreased conduction (i.e., reduced resistivity).

Thus, there remains a need for a heat transfer fluid composition thatresists corrosion, freezing, vaporization and gas adsorption, while atthe same time, provides long lasting performance and high electricalresistance.

SUMMARY OF THE INVENTION

One objective of this invention is to provide a heat transfercomposition for use in fuel cell assemblies.

It is another objective of this invention to provide a heat transfercomposition for use in fuel cell assemblies with high electricalresistance.

It is another objective of this invention to provide a heat transfercomposition for fuel cell assembly with electrical resistance greaterthan about 5 KΩ·cm.

It is another objective of this invention to provide a heat transfercomposition that confers corrosion protection.

It is another objective of this invention to provide a heat transfercomposition that confers freezing protection.

DETAILED DESCRIPTION

In order that this invention may be more fully understood, the followingdetailed description is set forth. However, the detailed description isnot intended to limit the inventions that are described by the claims.

The present invention provides heat transfer compositions for use infuel cell assemblies. More particularly, the present invention providesheat transfer compositions for use in fuel cell assemblies comprising:

(a) from about 0% to about 90% by weight alcohol;

(b) from about 1% to about 90% by weight polyalkylene oxide;

(c) from about 0% to about 50% additive by weight;

(d) balance being water.

Such heat transfer compositions are particularly well suited for use infuel cell assemblies to remove assuasive heat and maintain properoperating temperature while providing high electrical resistance.

The first component in the compositions of the present invention isalcohol. Suitable alcohols include monohydric or polyhydric alcohols andmixtures thereof. Preferred alcohols are methanol, ethanol, propanol,butanol, furfurol, tetrahydrofurfuryl alcohol (“THFA”), ethoxylatedfurfuryl, ethylene glycol, diethylene glycol, triethylene glycol, 1,2propylene glycol, 1,3 propylene glycol, dipropylene glycol, butyleneglycol, glycerol, monoethylether of glycerol, dimethyl ether ofglycerol, sorbitol, 1,2,6-hexanetriol, trimethylolpropane, alkoxyalkanols (such as methoxyethanol) and mixtures thereof. More preferably,the alcohol is ethylene glycol, 1,2-propylene glycol, 1,3-propyleneglycol, glycerol, tetrahydrofurfuryl alcohol and mixtures thereof.

The alcohol is present in the composition in an amount of about 0% toabout 90% (by weight), and preferably, about 20% to about 80%. Morepreferably, the alcohol is present in an amount of about 30% to about70%, and even more preferably, about 40% to about 60%.

The second component in the compositions of the present invention is apolyalkylene oxide. Polyalkylene oxides useful in the compositions ofthe present invention have an average molecular weight from about 55 toabout 380,000, and more preferably from about 135 to about 10,000.

Suitable polyalkylene oxides are polyoxyethylene (“EO”), oxypropylene(“PO”), oxybutylene (“BO”) polymers and mixtures thereof. Preferably,the polyalkylene oxide is a copolymer of EO and PO polymers having aweight ratio of EO to PO from about 1:100 to about 100:1, preferablyfrom about 1:3 to about 3:1. More preferably, the polyalkylene oxide isUCON LB-135, UCON LB-165-Y24, UCON LB-165Y3, UCON LB-165, UCON 1281,UCON LB-65, UCON 50-HB-55, UCON 50-HB-260, UCON 50-HB-100, UCON50-HB-5100, UCON 75-H-1400, UCON 75-H-90,000, UCON 50-HB-260-Y3, UCONHTF 500, LB165 Y24, LB165Y3; H1400, HB-100, HB-260, 50-HB-260-Y3,SYNALOX®, Polyglycol E200, Polyglycol E300, Polyglycol E400, PolyglycolE600, Polyglycol E900, Polyglycol E1000, Polyglycol E1450, PolyglycolE3350, Polyglycol E4500, Polyglycol E8000, Polyglycol E300NF, PolyglycolE400NF, Polyglycol E600NF, Polyglycol E900NF, Polyglycol E1000NF,Polyglycol E1450NF, Polyglycol E3350NF, Polyglycol E4500NF, PolyglycolE8000NF, MPEG 350, MPEG 550, MPEG 750, Polyglycol P-425, PolyglycolP-1200, Polyglycol P-200, Polyglycol P-4000, Polyglycol L-910,Polyglycol L-1150, Polyglycol 112-2, Polyglycol 15-200, PolyglycolEP530, Carbowax PEG 200, Carbowax PEG 300, Carbowax PEG 400, CarbowaxPEG 540 Blend, Carbowax PEG 600, Carbowax PEG 900, Carbowax PEG 1000,Carbowax PEG 1450, Carbowax PEG 3500, Carbowax PEG 4600, Carbowax PEG8000, Carbowax PEG 300 Sentry, Carbowax PEG 400 Sentry, Carbowax PEG 600Sentry, Carbowax PEG 900 Sentry, Carbowax PEG 1000 Sentry, Carbowax PEG1450 Sentry, Carbowax PEG 3350 Sentry, Carbowax PEG 4600 Sentry,Carbowax PEG 8000 Sentry, Carbowax MEG 350, Carbowax MEG 550, CarbowaxMEG 750, Polypropylene Glycol 425, Polypropylene Glycol 1025 andPolypropylene Glycol 2025 from Union Carbide/Dow Chemical, PLURACOLE200, PLURACOL E300, PLURACOL E400, PLURACOL E600, PLURACOL E1000,PLURACOL E1450, PLURACOL E2000, PLURACOL E4000, PLURACOL E4500, PLURACOLE8000, PLURACOL P410, PLURACOL P1010, PLURACOL P2010, PLURACOL P4010 andPluronic L-92 from BASF, POLY-G 200, POLY-G 300, POLY-G 400, POLY-GB1530, POLY-G 600, POLY-G 1000, POLY-G 1500, POLY-G 2000, POLY-G 300NF,POLY-G 400NF, POLY-G 600NF, POLY-G D400, POLY-G D1200, and POLY-G D2000from Olin; Silwet L-7200, Silwet L-7230, Silwet L-7600, Silwet L-7604,Silwet L-7607, Silwet L-7657, Silwet L-7650, Silwet L-7664, SilwetL-8600, Silwet L-8620, Silwet L-77, Formasil 891, Formasil 593, Formasil433, or Formasil 891 from Osi Specialties; or TBF-190 from PathSilicones, Inc.

Even more preferably, the polyalkylene oxide is UCON LB-135, UCONLB-165-Y24, UCON LB-165Y3, UCON LB-165, UCON 1281, UCON LB-65, UCON50-HB-55, UCON 50-HB-260, UCON 50-HB-100, UCON 50-HB-5100, UCON75-H-1400, UCON 75-H-90,000, UCON 50-HB-260-Y3, UCON HTF 500, LB165 Y24,LB165Y3; H1400, HB-100, HB-260, 50-HB-260-Y3, Pluronic L-92, PolyglycolP-425, Formasil 433, Formasil 891, Silwet L-7200, Silwet L-7230, SilwetL-7600, Silwet L-7604, Silwet L-7607, Silwet L-7657, Silwet L-7650,Silwet L-7664, Silwet L-8600, Silwet L-8620, Silwet L-77 or TBF-190.

The polyalkylene oxide is present in the composition in an amount ofabout 1% to about 90% (by weight), and preferably, about 2% to about75%. More preferably, the polyalkylene oxide is present in an amount ofabout 3% to about 50%, and even more preferably, about 5% to about 25%(by weight).

Preferably, the weight ratio of alcohol to polyalkylene oxide is about3:1, and more preferably about 5:1, and even more preferably about 15:1.

The third component in the compositions of the present invention is oneor more additives. Such additives include, dielectric fluids [e.g.,mineral, synthetic, and silicone fluids (e.g., Armul series from WitcoCorporation) or oils and mixture thereof]; wetting agents (Rhodafac PL-6from Rhodia); surfactants (e.g, Mazon RI or 14a series from BASF;Deriphat series from Henkel Chemical; Rhodameen T-15, Miranol CS Conc,Mirapol WT, Mirataine H2C-HA and Miramine TO-DT from Rhodia); antifoamand/or lubricants (e.g., polysiloxanes and polydimethylsiloxanes,Rhodafac PA-32, Lubrophos RD-570 and Lubrophos LB-400 from Rhodia;TBA4456 from Path Silicones, Inc.); solvents (e.g., Exxsol series fromExxonMobil); and corrosion inhibitors (TBF-77A and TBF-193 from PathSilicones, Inc.) and other additives known in the art that do notadversely affect the fuel cell assembly by reduction of electricalresistance.

The additive is present in the composition in an amount of about 0% toabout 50% (by weight), and preferably about 1% to about 30%. Even morepreferably, the additive is present in an amount about 2% to about 20%,and yet even more preferably, about 3% to about 10%.

Preferred compositions of this invention are described below.

One preferred composition comprises:

-   -   (a) from about 20% to about 80% by weight of an alcohol;    -   (b) from about 2% to about 75% by weight of a polyalkene oxide;    -   (c) from about 1% to about 30% by weight of an additive; and    -   (d) balance being water.

A more preferred compositions comprises:

-   -   (a) from about 30% to about 70% by weight of an alcohol;    -   (b) from about 3% to about 50% by weight of a polyalkene oxide;        and    -   (c) from about 2% to about 20% by weight of an additive; and    -   (d) balance being water.

An even more preferred composition comprises:

-   -   (a) from about 40% to about 60% by weight of an alcohol;    -   (b) from about 5% to about 25% by weight of a polyalkene oxide;    -   (c) from about 3% to about 10% by weight of an additive; and    -   (d) balance being water.

According to one embodiment, the heat transfer compositions of thepresent invention provide high electrical resistance. Such heat transfercompositions have electrical resistivity values greater than about 5KΩ·cm.

According to another embodiment, the heat transfer compositions of thepresent invention resist corrosion, freezing, vaporization and gasadsorption, while at the same time, provide long lasting performancewithout a change in electrical resistance.

The heat transfer compositions of the present invention can be preparedas concentrates. Such concentrates can be diluted with water.

The present invention also provides fuel cell systems comprising one ormore fuel cell assemblies and a heat transfer composition of the presentinvention. Such fuel cell assemblies are selected from the groupconsisting of PEMFC, PAFC, MCFC, SOFC and AFC.

The present invention further provides methods for removing heat from afuel cell assembly. Such methods comprise the step of contacting thefuel cell assembly, either directly or indirectly, with a heat transfercomposition of the present invention. Such fuel cell assembly isselected from the group consisting of from PEMFC, PAFC, MCFC, SOFC andAFC.

In order that this invention may be better understood, the followingexamples are set forth.

EXAMPLES

138 different heat transfer compositions were prepared (Examples 1-138).The components of these compositions are described in Tables 1-23 below.The abbreviations used in the tables below are as follows: Component Ais alcohol, Component B is polyalkylene oxide, Component C is additive,Component D is water, EG is ethylene glycol, PG is propylene glycol, Gis glycerol and THFA is tetrahydrofurfurol alcohol.

TABLE 1 Example No. Component (wt %) 1 2 3 4 5 6 Water 25 50 25 75Inorganic Antifreeze¹ 100 75 50 Organic Antifreeze² 100 75 50 ElectricalResistance 1.7 0.7 0.4 13 0.5 0.3 (KΩ · cm) ¹GM-4043M ²Havoline ExtendedLife Coolant

TABLE 2 Example No. Component (wt %) 7 8 9 10 11 12 A EG 100 75 60 50 APG 100 D Water 100 25 40 50 Electrical Resistance 0.9 5.9/2.2¹ 2.4 2.01.2 50/7.3¹ (MΩ · cm) ¹Resistance at 80° C.

TABLE 3 Example No. Component (wt %) 13 14 15 16 17 18 A PG 75 60 50 A1,3 Propanediol 100 75 60 D Water 25 40 50 25 40 Electrical Resistance3.6 2.2 1.1 33.3/11¹ 11.3 6.0 (MΩ · cm) ¹Resistance at 80° C.

TABLE 4 Example No. Component (wt %) 19 20 21 22 23 24 A 1,3 Propanediol50 A G 100 75 60 50 50 A PG 50 D Water 50 25 40 50 Electrical Resistance2.0 100 25/2.6¹ 15 5.7 100 (MΩ · cm) after ASTM D1384 1.0 ¹Resistance at80° C.

TABLE 5 Example No. Component (wt %) 25 26 27 28 29 30 A G 25 25 A PG 2525 A EG 25 50 B UCON LB-135 100 B UCON LB-165-Y24 100 B UCON LB-165Y3100 D Water 50 50 25 Electrical Resistance 2.3 3.0/1.0¹4.9 >100 >100 >100 (MΩ · cm) ¹Resistance at 80° C.

TABLE 6 Example No. Component (wt %) 31 32 33 34 35 36 B UCON LB-165 100B UCON 1281 100 B UCON LB-65 100 B UCON 50-HB-55 100 75 60 D Water 25 40Electrical Resistance >100 >100 >100 25 1.6 0.5 (MΩ · cm)

TABLE 7 Example No. Component (wt %) 37 38 39 40 41 42 B UCON 50-HB-5550 B UCON 50-HB-260 100 75 60 50 B UCON 50-HB-100 100 D Water 50 25 4050 Electrical Resistance 0.3 >100 3.7 0.7 0.3 100 (MΩ · cm)

TABLE 8 Example No. Component (wt %) 43 44 45 46 47 48 B UCON 50-HB-10075 60 50 B UCON 50-HB-5100 100 75 60 D Water 25 40 50 25 40 ElectricalResistance 4.0 0.7 0.3 100 1.5 0.2 (MΩ · cm)

TABLE 9 Example No. Component (wt %) 49 50 51 52 53 54 B UCON 50-HB-510050 B UCON 75-H-1400 100 75 60 50 B UCON 75-H-90,000 100 D Water 50 25 4050 Electrical Resistance 0.06 100 9.1 3.1 1.4 100 (MΩ · cm)

TABLE 10 Example No. Component (wt %) 55 56 57 58 59 60 CPolydimethysiloxane 100 C Octamethyltrsiloxane 36 CDecamethyltetrasiloxane 28 C Dodecamethyl- 17 pentasiloxane CPolydimethylsiloxane 17 C Vegetable Oil 100 C Soybean Oil 100 C Corn Oil100 C Castrol Oil 100 ElectricalResistance >100 >100 >100 >100 >100 >100 (MΩ · cm)

TABLE 11 Example No. Component (wt %) 61 62 63 64 65 66 A G 50 25 A EG25 50 B LB165 Y24 44 B LB165Y3 16 B H1400 5 5 C Petroleum Oil 100 CCottonseed Oil 100 C Pine Oil 100 C Soybean oil 40 D Water 20 20Electrical Resistance >100 >100 >100 >100 11.1 5.9 (MΩ · cm) after ASTMD1384 100 0.2 0.2

TABLE 12 Example No. Component (wt %) 67 68 69 70 71 72 A EG A G A PG 20B H1400 B HB-100 40 B HB-260 20 B UCON 50-HB-260-Y3 100 75 60 B UCON HTF500 100 75 D Water 20 25 40 25 Electrical Resistance 6.3 >100 9.1 3.48.3 (MΩ · cm) after ASTM 01384 1.0

TABLE 13 Example No. Component (wt %) 73 74 75 76 77 78 A THFA 100 BUCON HTF 500 60 B Pluronic L-92 100 50 C Mazon RI-4a 100 C Syltherm XLT100 D Water 40 50 Electrical Resistance 1.9 2.0 0.008 >100 0.1 >100 (MΩ· cm)

TABLE 14 Example No. Component (wt %) 79 80 81 82 83 84 C Syltherm XLT50 C Syltherm 800 100 50 C Rhodafac PL-6 100 50 C Rhodafac PA-32 100 DWater 50 50 50 Electrical Resistance 1.0 >100 11.1 0.2 0.04 0.5 (MΩ ·cm)

TABLE 15 Example No. Component (wt %) 85 86 87 88 89 90 C Rhodameen T-15100 C Deriphat 151C 100 C Lubrhophos RD-510 100 C Lubrhophos LB-400 100C Exxsol D 130 100 50 D Water 50 Electrical Resistance 1.3 0.3 0.40.5 >100 0.6 (MΩ · cm)

TABLE 16 Example No. Component (wt %) 91 92 93 94 95 96 B PolyglycolP-425 100 50 B Formasil 433 100 50 B Formasil 891 100 50 D Water 50 5050 Electrical Resistance 100 0.05 >100 1.2 1.3 0.03 (MΩ · cm)

TABLE 17 Example No. Component (wt %) 97 98 99 100 101 102 B Formasil593 100 B Silwet L-7200 100 B Silwet L-7230 100 B Silwet L-7600 100 50 BSilwet L-7657 100 D Water 50 Electrical Resistance >100 >100 >100 1000.2 1.4 (MΩ · cm)

TABLE 18 Example No. Component (wt %) 103 104 105 106 107 108 B SliwetL-7657 50 B Silwet L-7650 100 50 B Siwet L-77 100 50 D Water 50 50 50100 Electrical Resistance 0.03 100 0.4 1.2 0.1 0.4 (MΩ · cm)

TABLE 19 Example No. Component (wt %) 109 110 111 112 113 114 A EG 70 7070 70 70 70 B Pluronic L-92 5 B Polyglycol P425 5 C Syltherm XLT 5 CSyltherm 800 5 C Rhodafac PL-6 5 5 C Exxsol D130 D Water 25 25 25 25 2525 Electrical Resistance 1.5 1.5 2.1 0.03 1.6 0.8 (MΩ · cm)

TABLE 20 Example No. Component (wt %) 115 116 117 118 119 120 A EG 70 7070 70 A THFA 10 10 B Formasil 433 5 B Silwet L-7600 5 B Silwet L-7650 5B Silwet L-77 5 B 50-HB-260-Y3 45 50 D Water 25 25 25 25 45 40Electrical Resistance 1.6 1.0 1.8 1.0 0.7 1.1 (MΩ · cm)

TABLE 21 Example No. Component (wt %) 121 122 123 124 125 126 A THFA 30A 1,3 Propanediol 75 70 A EG 73.5 73.5 73.5 B 50-HB-260-Y3 30 5 BFormasil 433 4.4 B Silwet 7650 4.4 C Syltherm XLT 4.4 D Water 40 25 2522.4 22.4 22.4 Electrical Resistance 8.5 11.6 7.9 2.4 2.4 1.2 (MΩ · cm)After ASTM D-1384 1.1 0.8 0.04 0.04 1.0

TABLE 22 Example No. Component (wt %) 127 128 129 130 131 132 A EG 67 7070 70 70 A PG 67 B TBF-190 5 C TBF-193 5 C TBF-77A 5 C TBA-4456 5 DWater 33 33 25 25 25 25 Electrical Resistance nt nt 0.8 0.6 2.1 0.2 (MΩ· cm)

TABLE 23 Example No. Component (wt %) 133 134 135 136 137 138 A EG 74.9970 70 70 70 70 B Silwet L-7604 5 B Silwet L-7664 5 B Sliwet L-7607 5 BSilwet L-8600 5 B Silwet L-8620 C TBA-4456 0.01 5 D Water 25 25 25 25 2525 Electrical Resistance 2.2 1.4 0.8 1.6 0.7 1.0 (MΩ · cm)Measurement of Solution Resistance

Electrical resistivity, R, is defined in ASTM standard D 1125, as the acresistance in ohms measured between opposite faces of a centimeter cubeof an aqueous solution at a specified temperature. Electricalresistivity is measured by applying an ac drive voltage between parallelplatinum plates of known surface area and separation distance andmeasuring the resistance of the solution. The actual resistance of thecell, R_(x), is represented by the formula:R _(x) =R·L/Awhere L is the separation distance of the plates in cm, A is the crosssectional area of the plates in cm² and R is the resistivity of thefluid in MΩ·cm. Resistivity values greater than about 5 KΩ·cm areconsidered acceptable for fuel cell applications.

Solution resistivity measurements were made using a Traceable© BenchConductivity Meter 4163 with a glass platinum flow through probe. Theinstrument was calibrated to NIST (National Institute of Standards andTechnology) standards. The probe was initially rinsed with deionized(“DI”) water, dried and rinsed in the test solution to avoid dilutionand contamination of the test solution. The probe was immersed inapproximately 50 ml of test solution. Measurements were taken as theprobe was moved through the solution in a stirring motion. The stirringmotion helps to prevent polarization. Electrical resistivitymeasurements were made following ASTM test method D 1125.

Tables 1-23 show that the heat transfer compositions of the presentinvention provide high electrical resistance (i.e., electricalresistance values greater than about 5 KΩ·cm). For example, Examples35-37, 39-41, 43-45, 47-49, 51-53, 65-67, 69-70, 72-73, 77, 92, 94, 96,101, 103, 105, 107, 109, 114-121, 123, 125-126, 129, and 134-137 haveelectrical resistances of about 11.1 to about 0.03 MΩ·cm. In contrast,the control compositions containing inorganic antifreeze (Examples 1-3)or organic antifreeze (Examples 4-6) exhibit low electrical resistancesof 1.7 to 0.3 KΩ·cm.

Laboratory Modified ASTM D-1384—“Standard Test Method for Corrosion Testfor Engine Coolants in Glassware”

Thirteen heat transfer compositions were prepared and evaluated underthe conditions (modified as explained below) set forth by ASTM D1384.See Annual Book of ASTM Standards, section 15, Volume 15.05 (2000),incorporated herein by reference. ASTM D1384 is a standard test methodfor general corrosion of a variety of metals typically found in thecooling system and/or heating system of internal combustion engines.ASTM D1384 was modified in order to evaluate the metals that will beused in fuel cell assembly. Such metals include stainless steel,aluminum alloys and insulating polymers. ASTM D1384 was further modifiedso that the test formulations were not diluted with “corrosive water”(i.e., DI water containing 100 ppm each of SO₄ ⁻², HCO₃ ⁻ and Cl⁻, alladded as Na⁺ salts) Such dilution accounts for variations in water addedto traditional antifreeze concentrates, which may not occur with regardto fuel cell heat transfer fluids.

After preparing the compositions and subjecting them to the testprocedures set forth in ASTM D1384 (the metal specimens were immersedfor 336 hours in the heat transfer composition and maintained at atemperature of 88° C.), the weight change of the metal specimens weremeasured (average of duplicate measurements). A negative weight losssignifies a weight increase due to the formation of a protective coatingon the metal surfaces. A weight loss of 10 mg for each of copper, brass,steel and cast iron, and 30 mg for each of aluminum and solder is themaximum allowed to pass ASTM D1384.

As shown in Table 24, the heat transfer compositions of the presentinvention provide general corrosion inhibition for both stainless steeland aluminum. For example, Examples 66-67, 123 and 125-126 exhibitedstainless steel weight loss of <0.3 mg and Examples 65-67, 123 and 125exhibited aluminum weight loss of ≦10 mg. Table 24 also shows that theseformulations are effective general corrosion inhibitors for other metalscompared to water (Example 7), water/propylene glycol mixture (Example15 and 127), water/1,3 propanediol mixture (Example 122) andwater/ethylene glycol mixture (Example 128) in ASTM D1384.

TABLE 24 Metal Weight Loss (mg) Modified ASTM D1384 Stainless ExampleNo. Copper Brass Steel Steel Cast Iron Aluminum 7 2 5 219 nt 450 110 15−1.4 −1.1 5.3 nt 8.7 −1.0 15 −2.3 −1.8 nt −1.3 nt 1.4 64 0.2 −0.6 −0.4nt −1.1 −3.5 64 −1.9 −1.2 nt −0.7 nt −2.6 65 0.9 0.1 4.3 nt 24.8 −0.4 66−1.4 −1.2 nt −0.1 nt 5.5 67 3.6 0.6 139 nt 206 −2.7 67 0.1 0.6 nt 0.1 nt−3.1 122 2.7 1.1 7.4 nt 145 0.6 122 1.4 1.0 nt −1.3 nt 32 123 2.9 1.2 50nt 145 10 123 1.5 0.5 nt −1.6 nt 0.4 124 4.1 2.9 115 nt 254 0.3 124 4.12.2 nt 0.0 nt 1.8 125 1.5 2.7 82 nt 223 −1.6 125 2.6 0.3 nt −0.1 nt 1.8126 −3.8 −1.3 10 nt 230 −2.4 126 −2.2 −1.2 nt 0.3 nt 1.8 127 4 5 214 nt345 15 128 4 11 974 nt 1190 165 Nt - not tested; Examples 1, 128 and 129were tested under ASTM D1384 Test Requirements.

After completion of the modified ASTM D1384 test, electrical resistancewas measured for 10 heat transfer compositions (Examples 21, 64-67,122-126). As shown in Tables 11-12 and 21, the compositions of thepresent invention provide high electrical resistance even after exposureto different metal surfaces over extended test times. For example,Examples 65-67, 123 and 125-126 exhibit an electrical resistance ofabout 1 to 0.04 MΩ·cm after the ASTM D1384 test.

1. A heat transfer composition, comprising: (a) from about 20% to about80% by weight of an alcohol; (b) from about 1% to about 90% by weight ofa polyalkylene oxide; (c) from about 1% to about 30% by weight of anadditive; and (d) balance being water; wherein said composition has anelectrical resistance greater than about 5 KΩ·cm and wherein saidcomposition is used in a fuel cell assembly.
 2. The heat transfercomposition according to claim 1, wherein said composition comprisesabout 30% to about 70% alcohol.
 3. The heat transfer compositionaccording to claim 1, wherein said composition comprises about 40% toabout 60% alcohol.
 4. The heat transfer composition according to claim1, wherein said alcohol is selected from the group consisting ofmethanol, ethanol, propanol, butanol, furfurol, tetrahydrofurfuryl,ethoxylated furfuryl, ethylene glycol, diethylene glycol, triethyleneglycol, 1,2 propylene glycol, 1,3 propylene glycol, dipropylene glycol,butylene glycol, glycerol, monoethylether of glycerol, dimethyl ether ofglycerol, sorbitol, 1,2,6-hexanetriol, trimethylolpropane,methoxyethanol and mixtures thereof.
 5. The heat transfer compositionaccording to claim 1, wherein said alcohol is selected from the groupconsisting of ethylene glycol, 1,2-propylene glycol, 1,3-propyleneglycol, glycerol, tetrahydrofurfuryl alcohol and mixtures thereof. 6.The heat transfer composition according to claim 1, wherein saidcomposition comprises about 3% to about 50% polyalkylene oxide.
 7. Theheat transfer composition according to claim 1, wherein said compositioncomprises about 5% to about 25% polyalkylene oxide.
 8. The heat transfercomposition according to claim 1, wherein said polyalkylene oxide has anaverage molecular weight from about 55 to about 380,000.
 9. The heattransfer composition according to claim 1, wherein said polyalkyleneoxide has an average molecular weight from about 135 to about 10,000.10. The heat transfer composition according to claim 8, wherein saidpolyalkylene oxide is selected from the group consisting ofpolyoxyethylene, oxypropylene, oxybutylene polymers and mixturesthereof.
 11. The heat transfer composition according to claim 1, whereinsaid composition comprises about 2% to about 20% additive.
 12. The heattransfer composition according to claim 1, wherein said compositioncomprises about 3% to about 10% additive.
 13. The heat transfercomposition according to claim 1, wherein said additive is selected fromthe group consisting of dielectric fluids, wetting agents, antifoamagents, lubricants, surfactants, solvents and corrosion inhibitors. 14.A heat transfer composition comprising: (a) from about 30% to about 70%by weight of an alcohol; (b) from about 3% to about 50% by weight of apolyalkylene oxide; (c) from about 2% to about 20% by weight of anadditive; and (d) balance being water; and wherein said composition hasan electrical resistance greater than about 5 KΩ·cm and is used in afuel cell assembly.
 15. A heat transfer composition comprising: (a) fromabout 40% to about 60% by weight of an alcohol; (b) from about 5% toabout 25% by weight of a polyalkylene oxide; (c) from about 5% to about10% by weight of an additive; and (d) balance being water; and whereinsaid composition has an electrical resistance greater than about 5 KΩ·cmand is used in a fuel cell assembly.